In actual free market selling at loss is a very short-sighted strategy: you may cause the bankruptcy of your current competitors, but bariers to entry are low,

In actual free market selling at loss is a very short-sighted strategy: you may cause the bankruptcy of your current competitors, but bariers to entry are low, so once you raise your prices back to profitable levels the new competition arises. You would have to sell at loss most of the time which would eventually bankrupt your megacorp. That’s why monopolies can only exist in regulated markets.